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Rear ABS Sensors (again!)
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c6kev   
Wed Apr 20 2016, 05:54pm
Joined: Dec 02 2013
Member No: #1508
Location: Wales
 Like many before me, I have suffered from intermittent ABS/ESP/Hand Brake warnings. In spite of the warnings, all systems worked correctly. Lexia reported an intermittent rear left sensor fault so, after months of procrastinating, I got together with my local back street mechanic to replace both rear sensors.

Before dropping the fuel tank, we tried drawing a string from the connector under the right rear seat with the old wire. This turned out to be quite straightforward after removing just the rear tank support bolt and flexing the fuel tank slightly against its mountings. Drawing the new cable back through was equally easy. Total time to replace both sensors was less than one hour. But…….

With two new rear sensors, the warning lights are permanently alight. The ABS no longer works and the Parking brake is only applied for as long as you hold the lever (or wedge something under it). Cleaning both ABS rings has made no improvement. Lexia reports “invalid signal” with permanent fault codes C1335, C1325 (SC+, SC-, OC).

There is a suggestion in other threads that faulty sensor problems are more often caused by failure of the sensor connecting wires due to the long suspension travel of the C6.

Is it likely that both new cables have been damaged by our “cavalier” installation method?
Any recommendations on suitable wire that could be spliced in to effect a lasting repair?
Has anyone ever experienced problems with cheap aftermarket replacement sensors?
gmerry   
Wed Apr 20 2016, 08:19pm
Joined: Dec 11 2009
Member No: #21
Location: Scotland
 Hi, I replaced both rear sensors with Bosch units and so far touch wood, all problems fixed.

However, I went to the trouble of replacing the old rusty rear brake shields which were shedding copious ferrous debris over the sensors, and also the rear discs which were doing the same.

So my theory is that the sensors will be troublesome if operating in a sea of magnified sludge. Nothing to do with the suspension travel which is NOT long travel (assuming sensor wire is correctly routed and secured).

Regards
G

PS, I needed to dismantle the hubs to get the new sensors seated correctly. This involved cleaning up the corrosion etc. Are you sure they are in correctly?
c6kev   
Fri Apr 22 2016, 08:24pm
Joined: Dec 02 2013
Member No: #1508
Location: Wales
 After two days of cleaning the back plates and ABS rings and checking the wiring from end to end, I ordered another pair of sensors from Eurocarcare. Twice the price of the cheapies we fitted on Monday, but infinitely more useful. Everything is now running sweetly again.

Conclusion: Rear ABS sensors can be changed in an hour - but only if you buy decent quality parts!
gmerry   
Sat Apr 23 2016, 08:24am
Joined: Dec 11 2009
Member No: #21
Location: Scotland
 Hi Kevin, what was the brand of the cheapies and do you think they might have been fakes?

Regarding do the job using string and just easing the tank downwards, my take on it would be that the fuel filler neck should still be unbolted (under RH wheel arc liner) and the O ring removed from the filler neck because this is a very delicate part of the fuel tank and easily strained if the tank is eased downwards even just a little. But you have saved the considerable task of removing the exhaust system.

Regarding the brake protector, mine was 7 years old (6 Scottish winters of salty roads) and completely disintegrating. I can't imagine that other UK owners would find theirs in better condition. My advice, in my humble opinion, would be to do the job once, do it properly, remove the disks, replace the disc protectors and clean up the hub properly so the ABS sensors have a chance of working reliably.

Regards
G
c6kev   
Wed Apr 27 2016, 07:48am
Joined: Dec 02 2013
Member No: #1508
Location: Wales
 I posted the dodgy sensors back for a refund yesterday. No markings of any kind on the sensors, plugs or wiring. The packaging was just plastic bags with a part number (no manufacturer markings). The sensor heads themselves are slightly smaller diameter than both the originals and the latest replacements and are not an interference fit in the back plate - much easier to install and remove, but of no use whatsoever!

The original sensors which I removed from the car have part numbers on the sensor body (different left to right) but nothing to identify the manufacturer. The latest replacemenst are Delphi parts.

My disc protectorts were in good condition with minimal corrosion, but I don't know whether they are originals or not.

Regards,
gmerry   
Wed Apr 27 2016, 08:13am
Joined: Dec 11 2009
Member No: #21
Location: Scotland
 And the supplier for these poor ABS sensors was a little known auction site? with an unrecognisable seller?

Regards
G
Frode   
Thu Jul 29 2021, 09:56am
Joined: Jun 08 2017
Member No: #3171
Location: Bergen
 Hi,

I bought Bosch units to be safe, but the ABS fault did not disappear. After many, many hours and days searching for other possibilities, I found that the new sensor had the wiring reversed. A switch of wires, and everything worked. So, even high-end products may come with faults. Extremely annoying.

Best,
Frode
 

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